1. Field of the Invention
The present invention relates to a method and to a circuit arrangement for transmitting communication signals formed by data signals and/or signaling information between subscriber stations which are connected over switching centers of a first switching network operating with a first transmission procedure which, in particular, is formed by a line switching network or by a switching network enabling the transmission of communication signals in the form of packets, and a second switching network operating with a second transmission procedure differing from the first transmission procedure and enabling the transmission of the communication signals in the form of packets, whereby the transmission procedures of the switching networks participating in a connection are composed of network-independent procedure divisions containing the data signals and of the network-dependent procedure divisions at least containing the signaling information.
2. Description of the Prior Art
A circuit arrangement for transmitting digital signals over an exchange between transmission and/or receiving devices operating with different data transmission procedures and with different data formats is already known in the art, for example from U.S. Pat. No. 4,323,728, fully incorporated herein by this reference. The transmission of digital signals thereby occurs over a data switching center which is designed for handling different data transmission procedures and for the transmission of different data formats. Separate groups of termination circuits are provided for this purpose in the data switching center for the respective data transmission procedure and the respective data format. A conversion device is connected to the groups of termination circuits, the conversion device completely accepting the digital signals emitted by a termination circuit, intermediately storing said signals, and converting the signals in terms of data transmission procedure and data format and then emitting the converted signals to the respective termination circuit at the opposite side of the connection. This known circuit arrangement serves particularly for the transmission of digital signals between telex and teletex terminals.
In the transmission of digital signals over the converter device, there is no fixed connection between the terminals but, after the intermediate storage and conversion of the digital signals to be transmitted in the converter device, a plurality of communications with the terminals are required. Connected therewith, however, is a control expense in the converter device and in the connected data switching system which is, at times, not desired. In addition, it is not possible, given the converter device of the known circuit arrangement, to transmit communication signals between terminals which are connected to switching centers of a line switching network or a switching network enabling the transmission of communications signals in the form of packets and terminals connected to switching centers of a switching network enabling the transmission of communication signals in the form of packets, since the operation of such a converter device presumed that these converter devices would be equipped with corresponding packeting and de-packeting device which, in fact, however, is not the case. A further teletex/telex converter is also known from the publication "Philips Telecommunication Review", Vol. 39, No. 2, June 1981, which is fully incorporated herein by this reference. In this system, it is a matter of a converter which enables a transition from a line switching network into a packet switching network. However, executing a plurality of communications (a plurality of connection setup operations) between the terminals and the converter is also provided here in the transmission of digital signals between a telex terminal and a teletex terminal. Therefore, the disadvantage also arises in this system that considerable control operations are required within the converter or, respectively, within the exchange centers for the transmission of the digital signals.